| Graphene quantum dots were prepared by ultrasonic method, and theirfluorescence properties were investigated. The complex photocatalysts were designedto harness the visible spectrum of sunlight and phosphate sensor was constructed todetect the inorganic phosphate in bodies of water. In addition, several metal/siliconnanowire materials were synthesized, and the surface-enhanced fluorescencephenomenon of several luminescence rare earth ions in the presence of metal/siliconnanomaterials was studied. The main results are summarized as follows:(1) A facile ultrasonic route for the fabrication of graphene quantum dots (GQDs)is presented. The as-prepared GQDs exhibit an excitation-independentphotoluminescent (PL) behavior. And the complex photocatalysts (rutile TiO2/GQD andanatase TiO2/GQD systems) were designed to harness the visible spectrum of sunlight.It is interesting that the photocatalytic rate of rutile TiO2/GQD complex system is ca.9times larger than that of anatase TiO2/GQD complex under visible light (λ>420nm)irradiation in the degradation of methylene blue.(2) Graphene quantum dots were prepared by ultrasonic route and served as ahighly selective water-soluble probe for sensing of phosphate. The fluorescence ofGQDs was quenched by rare earth ion, europium (Eu+3) in proper concentration. Withphosphate added gradually, Eu+3ion progressively released from carboxylate modifiedGQDs and combined with phosphate. The recovered fluorescence is proportional to theconcentration of phosphate. The linear range for the detection of phosphate was8×10--7to9×10--6M with a detection limit of1.0×10--7M. In addition, the constructedsensor with simple, sensitive and cost-effective properties makes it valuable for furtherapplication.(3) The enhanced fluorescence of praseodymium ions (Pr+3) owing to resonantplasma oscillation on the surface of Ag/Si nanostructure was investigated. When Ag/Si nanomaterials were added, the fluorescence peaks were markedly enhanced. A typical12-to40-fold enhancement at604nm and18-to193-fold enhancement at640nmcould be achieved over a range of concentration from0.01to0.05M praseodymiumions, which had larger enhancement factor than that caused by unsupported silvernanoparticles. These results might be explained by the local field overlap originatedfrom the closed and fixed silver nanoparticles on silicon nanowires.(4) The surface-enhanced fluorescence of lanthanide ions (neodymium ions Nd+3,holmium ions Ho+3, and erbium ions Er+3) owing to resonant plasmons oscillation onthe surface of Ag/Si nanostructure was described. In the presence of Ag/Sinanomaterials, the fluorescence peaks were significantly enhanced, which resulted in atypical185-fold enhancement at592nm for Nd+3,82-fold at550nm for Ho+3and80-fold at533nm for Er+3at the concentration of0.05M. This Ag/Si nanostructure hadlarger enhancement factor than that caused by unsupported Ag nanoparticles, whichmight be attributed to the local field overlap originated from the closed and fixed Agnanoparticles on silicon nanowires.(5) The interaction of the surface plasmons of gold nanoparticles on siliconnanowires with fluorophores, lanthanide ions (Pr+3, Nd+3, Ho+3, and Er+3) wasinvestigated. In the presence of Au/Si nanomaterials, the fluorescence peaks weresignificantly enhanced, which resulted in about2orders of magnitude enhancement.The photoluminescence studies revealed that the enhanced fluorescence originates fromthe local field enhancement around Ln+3ions, caused by the electronic plasmonsresonance of the gold nanoparticles. Results showed that this Au/Si nanostructure hadlarger enhancement factor than that caused by unsupported Au nanoparticles. Theseresults might be explained by the local field overlap originated from the closed andfixed gold nanoparticles on silicon nanowires.(6) A method to enhance surface plasmon coupled fluorescence (SPCF) fromcopper nanoparticles on silicon nanowires substrate is presented. Owing to resonantplasmons oscillation on the surface of Cu/Si nanostructure, the fluorescence peaks ofseveral lanthanide ions (Pr+3, Nd+3, Ho+3, and Er+3) were markedly enhanced. Maximalabout2orders of magnitude enhancement could be obtained. This Cu/Si nanostructurehad larger enhancement factor than that caused by unsupported Cu nanoparticles. Theseresults might be explained by the local field overlap originated from the closed andfixed copper nanoparticles on silicon nanowires.
|
PDF Full Text Request